Associated Issues (HSC SSCE Chemistry): Revision Notes

Associated Issues

The chemical industry creates significant impacts across Australian society, the economy, and the environment. Understanding these associated issues helps us recognise both the benefits and challenges of chemical production, and how modern approaches like green chemistry aim to address environmental concerns.

Economic and social impacts

Australia's chemical industry makes substantial contributions to the national economy. The mining sector alone employs more than 2% of the Australian population across diverse roles, including engineers, chemists, truck drivers, and accountants. When combined with the broader chemical manufacturing sector that produces household and industrial chemicals for domestic use and export, employment numbers grow considerably.

The economic value is equally impressive. Australia's chemical manufacturing industry contributes approximately $11 billion to the national economy and represents 11.5% of the entire manufacturing sector. This demonstrates how integral chemical production is to Australia's economic health and employment landscape.

Energy in chemical production

Energy represents a major factor in all chemical production processes. Understanding where this energy comes from and how it's used helps explain both the costs and environmental impacts of the chemical industry.

Energy sources

Most energy used in chemical production comes from burning fossil fuels, including coal, natural gas, and petroleum. However, chemical companies increasingly turn to alternative sources when available. Hydroelectricity and other renewable energy sources offer two key advantages: they can be cheaper to use and they cause less environmental damage than fossil fuel combustion.

Energy uses in the industry

Chemical production requires energy at multiple stages, with some processes demanding far more energy than others. The following uses are listed in order of increasing energy consumption:

• Physical processes: Powering machinery for crushing and grinding raw materials requires the least energy
• Transportation: Moving materials via trucks, conveyor belts, or pipes demands moderate energy
• Heating processes: Roasting or evaporative processes like distillation require substantial energy to achieve the high temperatures needed
• Electrolysis: Breaking down chemicals through electrolysis of aqueous or molten solutions consumes the most energy

Understanding this hierarchy helps explain why chemical companies constantly seek more energy-efficient methods and why electrolysis processes are often located near cheap power sources.

Environmental issues

The chemical industry creates significant environmental impacts through both the production process and the use of final products. These impacts require careful management and increasingly strict regulation.

Consequences of acid rain

Acid rain forms when industrial waste products enter the atmosphere and react with water to create acids. This environmental problem illustrates how chemical production can have far-reaching consequences beyond the factory site.

Formation of acid rain

Although fossil fuels primarily contain carbon and hydrogen, they often include sulfur impurities. When these fuels burn, sulfur oxides form and subsequently react with atmospheric water to create sulfuric acid. The chemistry proceeds through these steps:

$2\text{SO}_2\text{(g)} + \text{O}_2\text{(g)} \rightarrow 2\text{SO}_3\text{(g)}$

$\text{SO}_3\text{(g)} + \text{H}_2\text{O(l)} \rightarrow \text{H}_2\text{SO}_4\text{(aq)}$

$\text{H}_2\text{SO}_4\text{(aq)} \rightarrow \text{H}^+\text{(aq)} + \text{HSO}_4^-\text{(aq)}$

Effects on aquatic environments

When acid rain falls, it travels into rivers, lakes, and other waterways through drainage systems and land runoff. The consequences for aquatic ecosystems can be severe and complex.

Many soils naturally contain negatively charged silicate ions that bind to various ions in the soil. Some bound ions benefit the environment (like magnesium and potassium), whilst others cause harm (particularly aluminium). When acid rain falls, the hydrogen ions displace these bound ions from the soil silicates. This releases harmful ions like aluminium, which then wash into nearby waterways.

The combination of low pH and increased aluminium ion concentration devastates aquatic life. Whilst some plants and animals can tolerate acidic conditions, many species are highly sensitive to pH changes. Young organisms and eggs face particular vulnerability. At pH 5 or below, fish eggs simply will not hatch. If pH drops even lower, adult fish suffer direct harm and die.

Crustaceans with calcium carbonate exoskeletons face a different but equally serious threat. The acid reacts directly with their shells, softening and potentially destroying them, leaving the animals defenceless. This reaction proceeds as follows:

$\text{CaCO}_3\text{(s)} + 2\text{H}^+\text{(aq)} \rightarrow \text{Ca}^{2+}\text{(aq)} + \text{H}_2\text{O(l)} + \text{CO}_2\text{(g)}$

When organisms die from these effects, the entire ecosystem suffers. Animals that depend on these organisms for food struggle to survive, and these impacts cascade through all levels of the food web.

Effects on forests

Acid rain also devastates forest ecosystems. Trees exposed to acid rain show slowed growth rates, leaves that turn brown, and eventually stopped photosynthesis. The damage occurs through multiple mechanisms.

Acid in the soil releases toxic ions like aluminium, using the same displacement process described earlier. This aluminium blocks the uptake of essential nutrients through tree roots, effectively starving the trees even when nutrients are present in the soil. In severe cases, entire forest regions in Europe and North and South America have died from prolonged acid rain exposure.

The image above shows the stark reality of forest devastation caused by acid rain, with dead standing trees stripped of foliage creating a skeletal landscape.

Effects on buildings

Human-built structures also suffer from acid rain. Limestone and marble buildings across Europe show severe damage from decades of acid rain exposure. The calcium carbonate in these building materials dissolves through the same chemical reaction that destroys crustacean shells (shown in the equation above). Over time, this dissolution causes significant structural damage and loss of architectural detail.

Chemical spills

Beyond ongoing emissions, the chemical industry faces serious environmental risks from accidental spills. These incidents can occur during production, transport, use, or storage of chemicals, and may result from fires, explosions, leaks, or damage to transport vehicles and storage tanks.

The Bhopal disaster

The Bhopal disaster of December 1984 stands as one of the worst chemical spills in history, demonstrating the catastrophic potential of chemical accidents. A gas leak at the Union Carbide India pesticide plant in Bhopal, India, exposed half a million people to methyl isocyanate and other toxic gases.

Methyl isocyanate is an extremely toxic chemical that causes severe problems through inhalation or skin contact. Exposed individuals can suffer chest pains and chemical burns. At high concentrations, the chemical causes pulmonary oedemas (fluid in the lungs), haemorrhages, and death.

Regulatory responses

The Bhopal disaster prompted worldwide reviews and implementations of emergency planning procedures. In the United States, legislators passed the Emergency Planning and Community Right-to-know Act. This law requires companies to provide detailed information about chemicals they use, store, and transport, and to submit comprehensive emergency plans for potential spills, leaks, and other incidents.

Addressing environmental issues

Recognition of these environmental problems has led to increasing regulation of the chemical industry. Several approaches now work together to reduce environmental harm.

Legislation and waste treatment

Modern legislation regulates how waste generated by chemical production must be treated and disposed of. The law now requires that waste can only be disposed of when it no longer harms the environment.

Liquid wastes from chemical plants must meet strict legislative requirements before release into sewage systems or waterways. Gases containing contaminants must pass through devices called scrubbers, which remove the majority of contaminants before the gases enter the atmosphere.

Green chemistry

A movement called green chemistry has emerged with the specific aim of reducing chemistry's environmental impact through fundamental changes to how we design and conduct chemical processes.

Green chemistry represents a relatively new field that aims to reduce environmental impact by minimising or eliminating the use or production of hazardous substances. As our understanding of chemical impacts on the environment grows, the importance of this approach becomes increasingly clear.

Origins and principles

The concept of green chemistry originated with the US Federal Pollution Prevention Act of 1990. This legislation established a hierarchy for addressing pollution:

1. Prevent pollution at the source
2. Treat chemicals to make them safe before disposal
3. Dispose of untreated chemicals safely

This hierarchy operates in order of preference. When designing a process, the primary goal is preventing pollution entirely. If hazardous chemicals cannot be avoided, they should be treated before disposal. Only if treatment proves impossible should untreated chemicals be disposed of (and then only through safe methods).

This systematic approach ensures that environmental protection receives priority at every stage of chemical production, rather than being an afterthought.